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If you click the third mouse (that is hidden under the scroll wheel) in other word-processing and pdf editors, this brings up an icon that shows up and down facing arrows (image attached). Placing the mouse pointer above or below this icon allows the document to scroll without any additional user ...

I am accustomed to clicking the 3rd mouse button and then moving the cursor to a position either above or below the 'double arrow' symbol that this generates to scroll quickly through a document.
This does not appear to be active/available in the BETA.